RU2391418C1 - Method of metal extraction from ore and device for method implementation - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: group of inventions refers to method of metal extraction from ores and device for method implementation. Method involves leaching by leaching solution with oxidiser, along with radiation of leaching solution by accelerated electrons of 50 keV to 1.7 MeV energy with rate adjustment for flow fed to leaching. Further metal is extracted from solution, and oxidiser is recovered in solution and recycled in leaching process. Device for metal extraction from ore includes vessel with leaching solution, vessel for leaching, chute connecting vessel with leaching solution and vessel for leaching, height adjustment unit for vessel with leaching solution, solution feed and drainage systems, and electron accelerator. The chute is used for transportation of leaching solution through electron accelerator zone, and height adjustment unit for vessel with leaching solution is used for leaching solution flow rate control. ^ EFFECT: intensified metal leaching from ores, reduced amount of chemical reactants and power consumption. ^ 2 cl, 1 dwg, 3 ex

Description

The invention relates to hydrometallurgical methods for processing ore raw materials and can be used, in particular, for the processing of hard-to-open uranium, gold, platinum and other ores in heap, agitation, vat and underground leaching.

To leach ore components, solutions of acids, alkalis and salts with oxidizing agents and reducing agents are used. The choice of solvents is determined by the selectivity of their action, the influence on the dissolution rate of certain minerals, particle size, concentration of reagents, temperature of the solutions and the duration of leaching. Reagents, as a rule, make up the bulk of the costs in the hydrometallurgical redistribution and determine the profitability of the use of chemical technologies (A.N. Zelikman, B.G. Korshunov. Rare metals metallurgy. Metallurgy, 1991).

Known methods for leaching intensification using strong oxidizing agents, oxygen purging, catalytic and special additives, with increasing temperature, etc. (RF patents No. 2087698, 2171855, 2172799) are associated with the costs of chemicals that lead to contamination with extraneous impurities, require additional operations or do not have the necessary performance, which ultimately leads to complications in the organization of production and the cost of the entire process.

Methods are also known for intensifying the opening of refractory ores, based on the physical action of ores by accelerated electromagnetic pulses with a short front (nanosecond) and electric field durations of the order of 10 ⁷ V / m, also accelerated electrons (Chanturia V.A., Bunin I.Zh. Modern Problems of Mineral Processing in Russia (Materials of the report at Miner's Week, 01/28/1999). However, despite the prospect of using the obtained results in hydrometallurgy, they have not yet found application on an industrial scale.

The closest set of essential features to the claimed one is a method for extracting uranium from ores, including leaching of uranium and iron with a solution of sulfuric acid using ferric iron contained in the ore as an oxidizing agent, extracting uranium from a solution to obtain a solution containing ferrous iron, and regenerating ferrous iron to trivalent oxidation to obtain a circulating solution and its recirculation to leach the ore, extracting uranium from the solution by sorption on the anio The solution obtained after sorption contains ferrous iron, before regeneration of ferrous iron in it, it is acidified to ferric iron by sulfuric acid and regeneration is carried out by irradiation with a stream of accelerated electrons at an absorbed dose rate of 2.3-3.5 kGy / s for 1-6 min ( RF patent No. 2326177, publ. 06/10/2008). In this method, due to electron irradiation, it is proposed to intensify the oxidation of ferrous iron to ferric iron in the process of regeneration of the circulating solution.

A device for the extraction of uranium from ores, consisting of a reaction chamber with a circulating solution with a mixing device, an electron accelerator, temperature sensors ("Intensive oxidant regeneration in the process of sulfuric acid leaching of uranium", Nesterov KN, Pirkovsky SA, Trusova V .M. Annotations of the reports of the 2nd International Symposium “Uranus”, M., November 2008, p.87). The disadvantages of this method and device are:

- the absence of a reasonable choice of the range of energies of accelerated electrons and, therefore, the types of accelerators that are best suited for hydrometallurgy of refractory ores;

-restriction of the possible use of radiation-chemical effects in hydrometallurgy only by the regeneration of the oxidizing agent of the leaching solution of uranium.

The technical result to which the invention is directed is the intensification of the method, reducing the number of chemicals, energy consumption, increasing productivity, reducing environmental pressure on the environment.

To this end, a method is proposed for extracting metals from ores, including leaching with a leach solution with an oxidizing agent using irradiation of the leaching solution with accelerated electrons, subsequent extraction of the metal from the solution and regeneration of the oxidizing agent in the solution with its leaching, while the leaching solution is irradiated with accelerated electrons with energy from 50 keV to 1.7 MeV with flow rate control when feeding it to leaching.

Also proposed is a device for the extraction of metals from ores, containing a tank with a leach solution, a leach tank, a supply and removal system of solutions and an electron accelerator, while it contains a tray connecting the tank with a leach solution with a leach tank for transporting the leach solution through the zone irradiation of the electron accelerator and the node for regulating the height of the tank with the leach solution to control the flow rate of the leach solution.

A key factor in achieving a technical result is the analysis of physical and chemical processes during the irradiation of liquid substances. Accelerated electrons in their interaction with these substances spend their energy on inelastic and elastic collisions, as well as on bremsstrahlung. At high electron energies, losses due to bremsstrahlung prevail, and at low energies, ionization and dissociation of atoms and molecules predominate. According to modern physical concepts, the removal of an electron from a neutral atom leads to the formation of a positive ion, from diatomic molecules to the formation of a positive molecular ion or is accompanied by dissociation of the molecule and the formation of fragmentation ions. In the case of polyatomic molecules, ionization and dissociation dominate. The maximum ionization cross section for most atoms and molecules is in the region of incident electrons, approximately 100 keV (Physical Encyclopedic Dictionary. M., “Soviet Encyclopedia”, 1983). The effectiveness of the chemical action of radiation is characterized by the value of the radiation-chemical yield G, which is the number of converted or formed molecules of a substance per 100 eV of absorbed energy. This value lies in the range from 1 to 20 molecules, i.e. one electron can cause several thousand structural transformations. With this energy, an electron can produce several ionization events, which are then significantly enhanced by secondary processes of collisions of ions and radicals. This is precisely the key to understanding the amplification of ionization processes during irradiation compared with electrolytic dissociation.

Thus, the electron energy from 50 keV to 1.7 MeV is optimal for intensifying the production of leaching oxidizing agents in any aqueous solutions. The upper limit is now mainly determined by the capabilities of accelerators, but because of the danger of inducing residual activity, it cannot be higher than the thresholds of photonuclear reactions on ore elements. In particular, for the ores under consideration, electron energies above 1.7 MeV are unacceptable (the threshold of the photonuclear reaction to beryllium).

The drawing shows the installation diagram of the accelerator for irradiating the solution, including the accelerator 1, the tank 2 with the leach solution passing through the tray 4 through the irradiation zone by an electron beam 3 into the tank for leaching 5. From the tank with the leach solution 2, the solution flows by gravity into the irradiation zone of the accelerator 1 while the flow rate, i.e. the residence time of the solution in the irradiation zone is controlled by a change in the height H and h.

The method is as follows.

The leach solution, which can be used acids, alkalis and salts, is irradiated with electrons at the beginning of the process.

From the tank with leach solution 2, it is sent to the tank for leaching 5, which are installed on both sides of the accelerator. In this case, the leach solution passes through the electron irradiation zone of the accelerator 1 along the tray 4. The flow rate, and therefore the residence time of the solution in the irradiation zone, which is necessary for the leaching process, is regulated depending on the change in the installation height of the vessel 2. All subsequent operations: metal recovery , for example, sorption, etc. are standard technological operations.

In our opinion, the ILU and ELV series accelerators designed and manufactured at the Institute of Nuclear Physics SB RAS (Salimov R.A. and others. ELV series accelerators and their use in radiation technological processes and medicine.Materials of the 10th International meeting in industry and medicine. St. Petersburg, 2001). In particular, these are the Fakel and ELV-12 accelerators with the following parameters, respectively: energy (0.5-0.8) and 1 MeV, beam power of 500 and 400 kW. The efficiency of these accelerators is 90%. The distinguishing qualities of accelerators are simplicity of design, ease of use and reliability. The control system includes a complex of hardware and software, covering all nodes of accelerators that require operational control, monitoring and diagnostics.

The performance of the device for operating the leach solution is estimated from the expression:

M = kPt / D,

where M is the mass of the leach solution after irradiation, kg;

k is the beam utilization coefficient,%;

P is the accelerator power, W;

t is the exposure time, s;

D is the specific absorption dose, Gy.

The specific absorbed dose is a function of the fluid flow rate, the width of the stream (tray), equal to the beam sweep width in the irradiation zone, electron mean radius and accelerator power:

D-KP / dRvn,

where d is the width of the stream, m;

R is the radius of the run, m;

v is the flow velocity, m / s;

n is the flux density, kg / m ³ .

Note that the flow rate is related to the height of the tank H + h relative to the horizontal scanning plane according to the free fall formulas.

The specific dose is determined by measuring the sufficient concentration of the leaching solution either at the operating radiation reactor or at low-power electron accelerators.

We show the possibility of implementing this method for the extraction of metals from refractory ores.

1. Acid leaching of uranium.

An aqueous solution of sulfuric acid and sulfate iron with concentrations up to 15 g / l and 10 g / l, respectively, is used as the leaching solution. In the classical method for intensifying leaching, the solution is purged with oxygen, hot steam, the temperature is raised to 150 ° C and various additives (pyrozulite, iron, etc.) are introduced into the solution. In industry, the cheapest sulfuric acid is most often used for opening ore:

U ₃ O ₈ + 4H ₂ SO ₄ + FeO ₂ > 3UO ₂ SO ₄ + FeSO ₄ + 4H ₂ O

According to our method, the leach solution without preliminary heating, purging with oxygen and steam, as well as without the introduction of special additives to enhance the oxidation processes, is fed into the tank for the initial leaching solution, from which it flows by gravity into the electron irradiation zone of the accelerator with an energy of 1 MeV and a beam power 400 kW When irradiated with electrons, ferrous iron is oxidized to ferric. Irradiation is carried out until, in the entire mass of the solution, the ratio of ferric to ferrous becomes equal to about 90%.

In addition to the generation of ferric iron and the O ₂ SO ₄ leaching complex, free oxygen, hydrogen peroxide, OH-type radicals, and other additives that enhance redox processes will be present in the solution as a result of electron irradiation. At the experimental value of the specific absorbed dose equal to 3.5 kGy, the leaching solution calculated according to the above formulas will be approximately 400 tons within 1 hour.

After irradiation, the solution is fed into the leach tank, followed by the process in any known manner.

Similar processes also occur during the leaching of uranium by the carbonate method.

2. Cyanide leaching of gold

As a leaching solution, an aqueous solution of sodium and potassium salts with their concentrations in solution of 0.2-0.3% is used. The process proceeds according to the reaction:

2Au + 4KCN + O / 2 + H ₂ O> 2K (AuCN) ₂ + 2KOH

The leaching ionic complex is the CN complex. From the reaction follows the need for the introduction of oxidizing agents into the process - additives in the working solution of oxygen, hydrogen peroxide, etc.

According to our method, the introduction of these and other oxidizing additives into the solution is not required, since all these additives will be intensively and constantly born in the solution during the intensification of leaching by electron irradiation.

Irradiation is carried out as follows: a solution of sodium or potassium cyanides, without any additives, is loaded into a container for the initial leaching solution, then this solution is fed into the irradiation zone of an electron accelerator with an energy of 1 MeV and a beam power of 400 kW, the operating time of the leaching ion complex is controlled, irradiation is stopped, as only the CN / KCN ratio will reach 0.9, and the solution is sent to the leach tank, followed by the process in any known manner. The residence time of the solution in the irradiation zone is controlled by changing the flow rate by changing the height of the installation of the tank for the leaching solution.

3. Thiosulfate leaching of gold and silver

The thiosulfate leaching process is based on the oxidation of gold and silver in an acidic environment with oxygen in the presence of sodium thiosulfate:

4Au + 8 (S ₂ O ₃ ) ^2- + O ₂ + 4H ⁺ > 4 [Au (S ₂ O ₃ ) ₂ ] ^3- + 2H ₂ O

4Ag + 8 (S ₂ O ₃ ) ^2- + O ₂ + 4H ⁺ > 4 [Ag (S ₂ O ₃ ) ₂ ] ^3- + 2H ₂ O

The leaching complex in this process is (S ₂ O ₃ ) ^2- .

Depending on the type of ore being processed and the content of gold and silver in it, the concentration of the leaching complex in the solution can vary from 2 to 60%. The introduction of oxygen and other additives into the solution by our method also does not make sense, since during the radiolysis of water and other components of the solution, oxygen and other oxidizing ions and ionic complexes will be formed in it. Irradiation by an electron accelerator with an energy of 1 MeV and a beam power of 400 kW is carried out in exactly the same way as described in the above examples, and it is stopped as soon as the ratio of the complexes Au (S ₂ O ₃ ) ^{2 -} or Ag (S ₂ O ₃ ) ^2- to S ₂ O ₃ will reach an acceptable value.

A priori, it can be assumed that the specific absorbed dose for all the examples considered by us will be close in value to the value of 3.5 kGy obtained experimentally, since the chemical and physical processes during irradiation of the solutions are essentially the same. When using the proposed accelerators, the production of leaching solutions will be approximately 400 t / h.

Thus, due to the intensification of oxidative processes according to this invention, the following technical results will be achieved:

- saving of chemical reagents due to a decrease in their quantitative composition in leaching solutions;

- saving energy costs due to the elimination of operations such as increasing the temperature and purging oxygen solutions, as well as due to the use of accelerator technology with high efficiency;

- reduction of environmental pressure on the environment due to the elimination of additives in solutions and a decrease in the quantitative composition of the reagents of these solutions;

- Opportunities have been created for the automation of leaching technology, at least for the automation of irradiation processes;

- increase the operating time of leaching solutions by increasing the number of modules of the radiation-chemical complex.

Claims (2)

1. A method of extracting metals from ores, including leaching a leach solution with an oxidizing agent using irradiated leaching solution with accelerated electrons, subsequent extraction of metal from the solution and regenerating the oxidizing agent in the solution with leaching, wherein the leaching solution is irradiated with accelerated electrons with energy from 50 keV to 1.7 MeV with flow rate regulation when feeding it to leaching. 2. A device for extracting metals from ores, containing a tank with a leach solution, a leach tank, a supply and removal system of solutions and an electron accelerator, characterized in that it contains a tray connecting the tank with a leach solution with a leach tank for transporting the leach solution through the irradiation zone of the electron accelerator and the node for regulating the height of the tank with the leach solution to control the flow rate of the leach solution.

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